African Journal of Environmental and Waste Management

African Journal of Environmental and Waste Management ISSN 2375-1266 Vol. 12 (2), pp. 001-008, February, 2025. Available online at www.internationalscholarsjournals.org © International Scholars Journals

Full Length Research Paper

Comparative Evaluation of MgSO4 and NaHCO3 for Extracting Available Phosphorus from Calcareous Soils

Fahad N. Assubaie

Department of Chemistry, College of Science, King Faisal University, P.O. Box 400, Al-Hassa - 31982, Saudi Arabia
E-mail: [email protected]; Tel: +966 554225521

Accepted 03 September, 2024

The effect of MgSO4 and MgCl2 on the release of available soil phosphorus was investigated and compared with the classical method of Olsen using NaHCO3. The experiments were carried out on soil samples from Al- Hassa oasis, Saudi Arabia. The soil samples were shaken with 0.004, 0.008, 0.5 M MgSO4, 0.5 M MgCl2 and 0.5 M NaHCO3. The results demonstrated that the amount of extractable phosphorus (P) by MgCl2 was lower than those extracted by NaHCO3 or MgSO4. Nevertheless, MgCl2 extracted P about 33% to 81% of that extracted by NaHCO3 and MgSO4 respectively. The application of different levels of P fertilizer did not significantly affect MgSO4 solution extractability. The correlation coefficients were 0.823, 0.908, and 0.879 for soil treated with 71.4, 142.9, 214.3 kg P2O5/h respectively. The original pH of MgSO4 solutions was 6.7 however, the pH of soil-MgSO4 suspensions slightly decreased with the increasing MgSO4 concentrations. On the other hand, the pH of soil suspension in 0.5 M MgSO4 increased with time, without shaking, reaching 7.6 within 24 h of incubation and then became stable. The same result was achieved when the soil suspension was shaken for 20 minutes. The pH of other MgSO4 concentrations became stable at 7.6 within 24 h. The amount of extractable P in the presence of MgSO4 increased with the increasing reaction time. The correlation coefficients between extracted phosphorus with 0.5 M NaHCO3 and that of extracted with 0.5 M MgSO4 after shaking for 20 and 30 minutes were 0.938 and 0.892 respectively. Accordingly, a 0.5 M MgSO4 solution can be efficiently used for extracting available phosphorus from calcareous soils, and without adjusting its pH. Moreover, its use will avoid the limitation of evolution of CO2 from NaHCO3 - basic extraction solution upon treatment with acidic molybdate for the determination of phosphorus.

Keywords: MgSO4, MgCl2, NaHCO3, phosphorus, calcareous soil.